The present invention relates to an electric monitoring method and apparatus for an electric system of an automotive vehicle in which an electric source in the form of a secondary battery is provided to supply a load current to an electric load circuit.
During use of the secondary battery, it is observed that the instantaneous terminal voltage across the battery decreases in accordance with increase of the load current under normal conditions. If the terminal voltage across the battery is extraordinarily decreased due to malfunctions of the load circuit, an alternator associated with the battery or the like, the life of battery is shortened. It is, therefore, desirable to monitor for an extraordinary decrease of the terminal voltage so as to hold the life of battery as long as possible.